Excel Desktop Slow to Open Files Sync'd via OneDrive

What does "slowly" mean: takes about 10 seconds to open an excel file (used to use an onpremise file server that apparently took 2-3s to open a file)
How users access the sharepoint files

  1. most sharepoint sites are sync'd via the OneDrive app (meaning they show up under the tenant name in file explorer - with the work icon)
  2. it also happens if you're using OneDrive online, and attempt to open a file in local app

Other Notes

  • we're using Files on Demand
  • we have selected "always keep on device" for the folder the file in question resides

Troubleshooting attempted:

  1. If you copy the file from the sync'd sharepoint site to c:\temp for example, it opens in 2-3s
  2. If you copy the file from the sync'd sharepoint site to your documents (which are backed up/sync'd by OneDrive as well) it takes ~10s
  3. If you quit onedrive (the file still resides on the PC due to it being stored on device), it opens in 2-3s. Once you start OneDrive again, it's back to ~10s
  4. If we "create a shortcut" to that sharepoint site (so it shows up as a link in OneDrive section of File Explorer instead of under the work/business side, it still takes ~10s to open
  5. if you open a PDF from the sync'd sharepoint site (not the shortcut, the business/work sync'd site), it opens in 2-3s (so this seems to be an issue for office apps only)
  6. If you open Excel (the primary file the users are worried about) in Safe Mode and navigate to the folder structure to find the file (this is a royal pain, I'd use it for troubleshooting, but not for production/day to day use), it opens in 5-7s (so better, but not as quick as it should) - this effectively also sidesteps a "disabling addins" step
  7. Multiple different PC's (spec'd as high as Core i5-1345u, 32gb ram, 2tb nvme ssd, windows 11), some fresh install of windows with no other software aside from default windows apps & office
  8. different internet connections (valley fiber [local isp], bellmts [local isp], tethered to rogers cell phone) with different routers & different security settings on said routers (home vs office vs cell phone)
  9. different internet connection types (ie. while in the office both on wired and wireless, at home on wired and wireless)